diff -r 000000000000 -r 6474c204b198 browser/metro/base/tests/mochitest/browser_test.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/browser/metro/base/tests/mochitest/browser_test.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,30 @@
+// Tests for the test functions in head.js
+
+function test() {
+  waitForExplicitFinish();
+  runTests();
+}
+
+gTests.push({
+  desc: "task sanity check",
+  run: function() {
+    let sum2plus2 = yield asyncSum(2, 2);
+    ok(sum2plus2 == 4, "asyncSum responded 2+2=4");
+
+    function asyncSum(a, b) {
+      var defd = Promise.defer();
+      setTimeout(function(){
+        defd.resolve(a+b);
+      }, 25);
+      return defd.promise;
+    }
+  }
+});
+
+gTests.push({
+  desc: "addTab",
+  run: function testAddTab() {
+    let tab = yield addTab("http://example.com/");
+    is(tab, Browser.selectedTab, "The new tab is selected");
+  }
+});